1. Field of the Invention
This invention relates to a focus adjusting device of a camera which can drive a phototaking lens by operation of a manually operated ring and also can drive the phototaking lens by the revolution output of a motor.
2. Description of the Prior Art
As a device of such type, there is known a focus adjusting device having a manual focusing mode for directing a phototaking lens to an in-focus position by operation of a manually operated ring and an automatic focusing mode for automatically directing the phototaking lens to the infocus position by the revolution output of a motor. This focus adjusting device is such that when a manual focusing mode is selected, a member for moving the phototaking lens in the direction of the optical axis thereof and a manually operated ring rotatable circumferentially of a lens barrel are coupled together by a meshing clutch to thereby enable focus adjustment to be effected manually and when an automatic focusing mode is selected, the member for moving the phototaking lens in the direction of the optical axis thereof and a motor producing a revolution output for automatically directing the phototaking lens to an in-focus position are coupled together by another meshing clutch to thereby enable automatic focus adjustment to be effected.
Generally, it is usual that the lens barrel has limit means for blocking movement of the phototaking lens in the direction of the optical axis thereof when the phototaking lens has come to an infinity in-focus position and when the phototaking lens has come to a very short distance in-focus position. Accordingly, even if a force which tends to drive the phototaking lens when the phototaking lens has come to the infinity in-focus position or the very short distance in-focus position is transmitted, in order that the limit member may not be destroyed by the driving force or in order that an intermediate mechanism for transmitting the driving force to the limit member may not be destroyed during the transmission of the driving force, the limit member and the intermediate mechanism must have their own suitable strength.
In the aforementioned conventional device, the force of the person who rotates the manually operated ring when the manual focusing mode is selected is intactly transmitted through the meshing clutch to the member for moving the phototaking lens in the direction of the optical axis thereof and the revolution force of the motor is intactly transmitted through another meshing clutch to the member for moving the phototaking lens in the direction of the optical axis thereof when the automatic focusing mode is selected and therefore, where it is intended to provide this device with the above-mentioned limit member, the limit member and the intermediate mechanism must be made to have such strength that can withstand both the force of the person who rotates the manually operated ring and the revolution force of the motor. The force of the person who rotates the manually operated ring is much greater than the revolution force of the motor which effects focus adjustment and therefore, where it is intended to provide the conventional device with the limit member, the strength of the limit member and the intermediate mechanism must be set so that they can withstand the force of the person who rotates the manually operated ring. Accordingly, when it is intended to provide the aforementioned conventional device with the limit member, the limit member and the intermediate mechanism will become bulky to secure the strength thereof and necessarily, the entire device will become bulky.